1. Field of the Invention
This invention relates to an electric switch means, and more particularly to a switch means employed in a camera for controlling an exposure control circuit in the camera body.
2. Description of the Prior Art
In an automatic exposure control camera including an electric circuit for controlling exposure time, there is usually employed a mechanical switch consisting of a pair of electric contacts made of elastic conductive material each having an inwardly projecting portion near the free end thereof. This kind of mechanical switches are apt to cause malfunction owing to the particular structure thereof including the sharply formed projecting portions and/or the characteristics of the material which is liable to be oxidized or to which dusts and stains are liable to stick. Further, this kind of mechanical switches have a defect in that when they are manually operated they will chatter however softly may they be touched and it will usually take about 3 milliseconds for the switch to be stabilized. The chattering of the switch will cause malfunction of the exposure control circuit including the switch. Particularly, in the exposure control circuit associated with a complicated mechanism for controlling complicated shutter and other mechanisms in the camera in which a number of switches are operated in a short peiod for sequentially controlling various mechanism in a determined order, the chattering of switches is a serious problem which is concerned with the results of photographing.
In order to eliminate the malfunction of the switches, for instance, gold contacts are employed in some switches. However, this kind of improved switches are still disadvantageous in that the contact resistance thereof will increase as the time lapses and dusts and stains are likely to stick thereto and further the price thereof is high.
In addition, the conventional mechanical switches or sealed lead relay switches occupy a large space and consume electric current to some extent. The photographic cameras are desired to be made compact in size and small in weight as much as possible, and accordingly, it is undesirable that a complicated switch means occupying a large space be incorporated in a camera body. Further, the power consumption by the switches is desired to be made as small as possible.